Apatite from Perth, Ontario, Canada. Specimen is approximately 4 inches (10 centimeters) across.
Uses Manufacture of fertilizer - it is a source of phosphorus. Occasionally used as a gemstone. Apatite also serves as an index mineral of Mohs hardness scale with a hardness of five.
Color green, brown, blue, yellow, violet, colorless
Streak white
Luster vitreous to subresinous
Diaphaneity transparent to translucent
Cleavage poor
Luster vitreous to subresinous
Hardness 5
Specific Gravity 3.1 - 3.2
Distinguishing Characteristics easy to recognize by color, crystal form, and hardness, can be scratched with a steel knife blade
Crystal System hexagonal
Chemical Classification phosphate
Chemical Composition a variety of calcium phosphates: fluorapatite: Ca5(PO4)3F, hydroxylapatite: Ca5(PO4)3(OH), chlorapatite: Ca5(PO4)3Cl, carbonate-rich apatite/francolite: Ca5(PO4,CO3)3(F,O)

Apatite is a group of phosphate minerals which includes: fluorapatite, chlorapatite, hydroxylapatite, carbonate-rich apatite and francolite. The term "apatite" is often used for fluorapatite, the most common of these minerals. Apatite is found in igneous, metamorphic and sedimentary rocks. The most extensive deposits are the sedimentary "phosphate rocks", which are mined to produce phosphate fertilizer.